No one regularly shoots one hole groups with "cheap" ammo, regardless of the rifle. Inexpensive ammo is not consistent enough to achieve such results. Otherwise we would see them often on the five 5-shot half-inch or better groups at 50 yards thread.
That said, the CZ 453 Lux is not guaranteed to be any more or less accurate than any other CZ rimfire, whether it is a 455, 452, or a 453. No model has hold on being more accurate than the other. The 455's may have more problems among them but that is another story. The key to accuracy for any CZ is in the barrel. The advantage that the stock 453 has is its set trigger, which when set is usually less than a pound. The 452 and 455 can be easily modified with a spring swap to achieve a very light trigger pull. The set trigger is the key difference between the 453 and the other bolt action models -- that and the fact that all the 453's have the same action screw configuration that is not shared by the others. The main point is the set trigger does not in itself make the 453 a more accurate model.
The key for shooting the Lux with its narrow fore stock is to have a front rest bag that matches the fore end. Better still is to place the front bag just forward of the magazine well where the stock is still relatively wide and flat. That will allow for more stability off the bench.